There is a battery charging device for use on a vehicle or the like that charges a battery by converting an alternating current generated by an alternating-current generator operating in association with the engine into a direct current by means of a switching element and applies the direct current to the battery (see Japanese Patent Laid-Open No. 2012-39817, for example).
The conventional battery charging device determines an energization phase angle that defines the timing of energization of the switching element for supplying a charging current from the alternating-current generator to the battery, and controls the energization of the switching element based on the energization phase angle.
In this way, the charging current is supplied from the alternating-current generator to the battery.